1. Field of the Invention
This invention relates to turbine-condenser configurations, and more particularly, to means for structurally connecting them so as to permit relative movement therebetween and minimize the condenser vacuum load on the turbine's supporting foundation.
2. Description of the Prior Art
The last stages in low pressure central station steam turbines typically operate at subatmospheric pressures and thus cause the turbine casing to be subjected to large atmospheric pressure forces which have commonly been balanced by the turbine's supporting structure. Subatmospheric pressure steam condensers for large central station applications are usually arranged beneath the low pressure turbines and their supporting structures and are connected to the low pressure turbines through flexible expansion joints which permit relative motion between the connected turbine and condenser while preventing atmospheric leakage into the condenser. The aforementioned condenser usually has its own support structure for bolstering the operating weight of the condenser and condensate accumulated therein. Such condensers normally have a net unbalanced pressure force directed toward the turbine in the upward direction, but that force is substantially reduced by the weight of the condensate which collects in the bottom or hot well of the condenser.
Traditionally, the support structure for large central station turbine generator units has consisted of reinforced concrete. In the past, there has generally been insufficient incentive for using alternate types of foundation structure, either to effect cost savings or to reduce foundation size and weight. Recently, however, a new concept in central station power generation has evolved. The new concept includes launching large sea-going vessels containing power generation equipment, such as turbines, condensers, etc. Support of such turbines necessitates use of relatively lightweight structures such as steel or other high strength structural components. As such, it has become important to minimize the size and weight of such turbine supporting structures while maintaining the supportive capabilities necessary to bolster large central station turbines and associated apparatus.
Copending Westinghouse Electric U.S. Pat. No. 4,189,926 which was filed June 15, 1978, and whose Ser. No. is 915,690, illustrates a vacuum balance chamber having an internal and an external wall with the external wall providing flexing capability and the internal wall preventing intrusion into the chamber of liquid condensate. Since the outer wall flexes in the copending patent application, the structural support columns which connect the outer wall to the turbine must pass through the vacuum balance chamber's inner wall and must be provided with means for preventing condensate intrusion into the chamber. A disadvantage of the aforementioned structure is the undesirable possibility of accumulating condensate within the vacuum balance chamber. Such condensate accumulation can adversely affect the pressure force balancing dynamics and may necessitate supplementary condensate drains from the vacuum balance chamber. Additional disadvantages of the copending patent application include the necessity for maintaining fluid communication from within the condenser or turbine exhaust neck to the vacuum balance chamber, the relatively high structural support columnar strength required, and the increased height requirements of the condenser when the aforementioned configuration is utilized. The copending application's vacuum balance chamber's expansion joint can, under certain foundation conditions, be difficult to assemble and relatively inaccessible for inspection and maintenance. Additionally, the goal of providing a good liquid seal between the vacuum balance chamber's inner wall and the intersecting structural support columns and the goal of permitting free, unrestrained movement therebetween are difficult to simultaneously achieve and can result in some sacrifice in one to satisfactorily obtain the other.